What's stopping you from writing a sourcemap module and publishing it on npm? I don't think there's anything in the sourcemap spec that requires it to be the a core module but please correct me if I'm wrong.

Rather, I'd like to node to understand source-mapping information. How can we see correct line numbers and file names in runtime error messages when we use CoffeeScript? That's sourcemap and it is the interpreter which can process source-mapping files.

... this would also help for development in terms of bringing the Node debugger closer to browser debuggers in terms of feature parity -- making it a bit more viable to develop and test libraries in just Node instead of in Chrome.